FDS lifetime

[Challen]

Hi, I use SDK13.1 FDS example and have some questions about that. Is there any influence about the lifetime of Flash when i use FDS function to write and delete the records.If it has,how to calculate the lifetime of Flash.Thanks.

[MartinBL]

Hi,

The flash in the nRF52 series should tolerate minimum 10,000 write/erase cycles (specs) and the FDS library has a basic wear leveling mechanism to avoid wearing down the flash too soon. The lifetime of the flash depends on how much flash you allocate to the FDS library. Say for example that you only allocate one single page. Then old data will have to be overwritten much sooner than if you allocated e.g. 5 pages, effectively reducing the lifetime. Note also that the FDS records has some overhead.

Bottom line; assign as many pages you can to the FDS library, and try to minimize the effect of the overhead by storing as much data as you can in each record. In the end, how long your flash will last depends on your implementation and is hard to calculate without intimate knowledge of your application.

[3Rsteven]

hi MatinBL

i try to do simple Calculation with FDS lift time. is it right?(only two page ,

on nrf52(one page is 4096B)

with base case , only two page (one data and swap). to asset the swap page erase/write count about lifttime.

if every one minute ,and save one work data. with 2 page(1 data and 1 swap) ,do gc when full update

one FDS Record = TL Part+ IC Part+ Record ID and data(1W) ,is 4 words . 

the data page and swap page 2Word, 0xDEADC0DE F11E01FE and 0xDEADC0DE F11E01FF

 1. every page should be update 255 times/minute, 1024W - 2W(header) / 4 =255 (4.25 hours)

 then swap page and one of data page ,do fds_gc(erase then write ) 

2. Suppose 4.25 x ~10000(nrf52 minimum 10000 write/erase) , it should be about 5 years(4.9189).

3. if more than data page ,it will more and more ?